Your mum is trying to make your son have a comforter? That's weird. Surely they decide there selves if they want something, have you stopped giving him a dummy or does he not want one. My ds constantly has a muslin, but he's only 7 months. Plays with it, naps with it and has one at bed. The good thing is he doesn't care which one he has (at the moment) as they are all the same. Forcing a toy that there I only 1 off seems strange. I've only heard of one child suddenly having a comforter at about 3, and it happened as her friend had one.

'Transitional objects' - which is what comforters are, can be useful to help a child move between situations that they may be uncertain about. It is something that helps them to feel safe because it is associated with home/somewhere safe. DD1 has a teddy that went everywhere with her for about 2 years. It was really helpful when DH went back to uni and everything was really uncertain in her life. DD2 loves her muslins - these are a lot easier to handle as she's isn't specific (we had to be super vigilant about teddy....). However, it only works or is useful if the child chooses it themselves. Some children don't need them or find comfort in something else. If he does choose something, make sure you get a duplicate (we didn't and I regret it - persuading an 18month old manky, smelly, vomit covered teddy was not the easiest challenge...!)

I have three children and never really bothered with this sort of thing...always reminded of my brother and his festering blankie!!

hell to pay if it was washed or missing

So once they were old enough to want to take things out, I just explained that it might get lost, and it was best to stay at home. Ds1 had a vile purple nylon shiney dinosaur for his favourite, but never out of the house.

Our nursery encouraged us to give DD a "muzzie" (muslin cloth) as a comforter, but she was much younger when we did it than your DS. It worked really well and she still uses a muzzie at bedtime. Obviously they are washable and interchangeable, so we don't have to worry about losing them. She will only accept John Lewis ones, as she is a girl after my own heart. She doesn't take them out any more (3 yo).

DS is 19 months and has never had a dummy (despite one being offered) or a comforter (despite various offerings). He is starting to get a fondness for Igglepiggle now, but I think that's more about the noises he makes .

DD had the lot, finally weaned her off her dummy at about 3, and strangely she lost interest in Gerry the Giraffe at the same time (Gerry was precious, we had 2, and he only left the house for long car journeys!!)